Spark plug



P. A. DOYLE SPARK PLUG Filed July 24, 1937 Ava furor: Pfizer A. Dan:

J/ wav/w flrronvex July 4, 1939.

Patented July 4, 1939 UNITED STATES PATENT OFFICE SPARK PLUG ApplicationJuly 24, 1937, Serial No. 155,397

1 Claim.

My invention relates to spark plugs, and has for its principal object toproduce a spark plug particularly adapted to high compression, highspeed, gasoline engines, and in which the spark is always operative inits full intensity. Another object is to produce a spark plug in whichthe negative electrode is provided with a disk-shaped member adjoiningits free end, whereby the movement of the turbulent gases in the upperportion of the engine cylinder adjacent such diskshaped member islessened and the sparking between the positive and negative electrodesis not substantially interfered with by reason of such turbulence.

The high compression generally developed in gasoline engines forautomobiles is partly responsible for the inefficiency of spark plugs ofthe usual type now on the market. By my new spark plug with thedisk-shaped member adjoining the free end of the negative electrode Iovercome such inefficiency and produce a spark between the positive andnegative electrodes that is of full intensity and delivered at regularintervals. For the smooth operation of a high speed gasoline motor it isessential that the spark delivered by the spark plug be absolutelyregular and of such intensity as to ignite the gases entering the enginecylinder from the manifold, and in some types of spark plugs with whichI have had experience, as the compression in the motor increases theefficiency of the spark plug decreases.

Fig. l is a cross-sectional view of my improved spark plug.

Fig. 2 is an enlarged side elevation of the lower portion of my sparkplug.

Fig. 3 is an enlarged bottom plan view of my improved spark plug.

Fig. 4 is an enlarged side elevation, similar to Fig. 2 but taken from adifferent angle.

Fig. 5 is a perspective view of a negative electrode element.

In the invention as illustrated in the drawing, the detachable shell Ii]is provided with the usual longitudinal bore II to receive the porcelaininsulated, cylindrical positive electrode-carrying member I2, in whichis centrally located longitudinally of said member I2 the positiveelectrode I3. On a shoulder I4 in the bore II of the shell I0 is locateda packing washer I5 against which a shoulder I6 on the lower portion ofthe porcelain member I2 is adapted to seat. The porcelain member I2 hasanother shoulder II on which a packing washer I8 is adapted to seat andon which a cylindrical plug I9 is seated by virtue of the screw-threadedportion 20 on the plug I9 and the screw-threaded portion 2| in the shellI0. By these means the member I2 is firmly and positively seated in theshell I0.

At the top of the porcelain member I2 and contacting with the electrodeI3 is a copper element 22 exteriorly screw-threaded, as at 23, toreceive an interiorly screw-threaded member 24, whereby electricalcontact with the battery (not shown) is made. The structure which hasjust been described is substantially common to all spark plugsordinarily employed for use in gasoline engines for automobiles.

The shell l!) acts as a negative electrode for the spark plug and isgrounded through the engine and frame of the automobile or other devicesupporting the engine, as is now commonly done. To the lower end of theshell I0 a negative electrode extension piece 25 is secured, preferablyby welding 25'. The negative electrode extension piece 25 is acontinuation of the shell I0, and the free end 26 of said negativeelectrode extension piece 25 is separated from the positive electrode I3by approximately 7 of an inch. Near the end 26 of the negative electrodeextension piece 25 is a disk-shaped portion 21, which may be formed onthe electrode extension piece 25 as an integral part thereof, or it maybe provided with a central perforation 28 of a size sufficient to slipover the circular electrode extension piece 25 and be secured thereto bywelding.

The shell ID at the lower portion thereof is provided with screw-threads29 adapted to engage with screw-threads in the upper portion of thegasoline engine cylinder (not shown). When my improved spark plug ispositioned in a gasoline engine cylinder, the disk 2'! acts as a barrierto the flow of gases and tends to break up such flow so that there is arelatively unobstructed flow of electric current between the positiveelectrode I3 and the negative electrode 25. This is highly important inorder that the passage of the spark produced by the electric currentpassing from the positive electrode I3 to the negative electrode 25 bepermitted to take place when contact with the battery is established,and that such sparking be regular and of full electrical intensity,particularly in high speed motors.

In the use of my improved spark plug I ignite all of the gases, and byreason thereof I produce increased mileage for the gasoline consumed inthe operation of an automobile. I also decrease the formation of carbonby my improved spark plug.

If a spark gap consisting of two more or less pointed electrodes issubjected to a high voltage,

an electrostatic field is set up in the gap. The distribution of thisfield is not uniform throughout the length of the gap, as theelectrostatic lines of force will be crowded together very closely inthe immediate vicinity of the electrodes and spread out to a maximumseparation in the gap midway between the two electrodes. Theconcentration of these electrostatic lines of force is a measure of thedegree of electrical stress to which the air in the gap is subjected. Ifthe concentration exceeds a certain amount, the air breaks down(ionizes) and becomes conducting. This break-down manifests itself by abluishviolet glow, known as corona.

When a high voltage is applied to agap of the type being discussed,corona is first formed around the tips of the electrodes. This, ineffect, shortens the gap between the electrodes, the ionized air wherethe corona occurs being equivalent to an extension of the electrodes.The effective length of the air gap having thus been shortened, theremaining length of air column is unable to withstand the impressedvoltage and breaks doWn with the characteristic spark discharge.

In the case of electrical ignition, the initial production of corona(which has no igniting properties because of its relatively lowtemperature) represents a dissipation of electrical energy and thusreduces the amount of energy available to produce the spark, reducingthe calorific value of the latter accordingly.

In my invention, the disk 21 serves to reduce the concentration of theelectrostatic lines which would otherwise have taken place around thetip of electrode 26, and allows these lines to fringe outward anddistribute themselves over the surface of the disk. While theelectrostatic field will still have its greatest density at the tip ofelectrode 26, the concentration will be much lower. This serves toreduce the initial production of corona, resulting in a reduced time lagand a more intense spark of higher ignition properties.

While I have illustrated and described the positive and negativeelectrodes generally employed in spark plugs, it will be understood thatthese polarities may be reversed without in any Way alteringtheoperation of my invention.

I claim:

A spark plug comprising a shell constituting a negative electrode, apositive electrode extending centrally and longitudinally through aporcelain insulated member positioned in said shell, said shell havingan electrode extension piece extending beyond one. end thereof, saidpositive electrode and said extension piece on said negative electrodebeing separated to provide a sparking gap, said extension piece beingbent at a right angle to itself, and a disk-shaped piece on said angularportion of said extension piece adjacent the free end of said angularportion of said extension piece for the purpose of reducing theconcentration of the electrostatic field at the tip of said extensionpiece.

PERCY A. DOYLE.

